BACKGROUND: The long-term maintenance of antiretroviral therapy (ART) remains an important issue, especially in limited-resource settings where additional barriers exist. A cross-sectional study was performed 24 months after ART initiation for patients treated in Cambodia in order to estimate the prevalence and identify determinants of non-adherence. METHODS: Adults receiving ART for 24 +/- 2 months were considered eligible for the study. Self-reported non-adherence was defined according to an algorithm based on six items. The questionnaire also assessed ART-related side effects and HIV disclosure. HIV-1 RNA plasma viral load was measured using real-time PCR. Multivariate rare events logistic regression analysis was used to identify independent factors associated with non-adherence. RESULTS: A total of 346 patients participated in the study. At 24 months, 95% of patients were adherent, 80% had HIV RNA <40 copies/ml and 75% had CD4+ T-cell counts >200 cells/mm3. Virological success was significantly higher in adherent patients than in non-adherent patients (81% versus 56%, P=0.021). Living in a rural area, limited HIV disclosure and perceived lipodystrophy were independently associated with non-adherence. CONCLUSIONS: At 24 months, adherence to ART was high and explained positive virological outcomes. In order to maintain adherence and long-term virological benefits, special attention should be given to patients living in rural areas, those with lipodystrophy-related symptoms and others who express difficulties disclosing their condition to close family members.